Respiratory Disturbances During Sleep Increase with Age

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BOSTON -- The frequency of breathing irregularities during sleep started to increase after age 50 in completely healthy individuals and rose dramatically after 65, a study found.

However, such disturbances may be part of normal aging, leaving open the question of whom to treat for obstructive sleep apnea, Steven A. Shea, Ph.D., of Harvard, and colleagues reported in the Feb. 1 issue of Sleep.

Polysomnographic respiratory abnormalities have been extensively studied in the general population, but studies have not targeted completely healthy individuals, the researchers said. Furthermore, they said, the criteria and measuring techniques have changed since the earlier studies were done.

Action Points

Explain to interested patients that respiratory disturbances during sleep increased dramatically with advancing age in healthy individuals without signs of obstructive sleep apnea.

Explain that it was not possible to determine whether these individuals should be evaluated and treated, leaving the clinical decision to individual physicians.

In a study spanning four years, the researchers did a cross-sectional analysis of 163 consecutive healthy volunteers (106 men, ages 25 to 71) who were given elaborate screening for chronic illness, drug and alcohol dependence, and psychiatric history. Obese individuals and those taking medications were excluded.

Eligibility for inclusion in the study was confirmed by extensive questionnaires, physical examination, electrocardiography, and sleep lab analysis.

Historically, the researchers noted, in other studies that used advertisements for healthy study participants, only about 5% of individuals who responded reached this final stage of recruitment. Thus, these volunteers represented a highly selected group of currently completely healthy individuals, they said.

After selection, the volunteers underwent full nocturnal polysomnography in an accredited sleep laboratory using current standard recording and scoring techniques.

Most volunteers completed an additional sleep questionnaire concerning sleep habits and symptoms and were asked whether they snored.

In addition, the polysomnographic technician reported whether or not any snoring was heard via a microphone placed next to the person's bed.

There was a remarkable increase in respiratory disturbances with age, particularly after 50, the researchers found.

For example, only 5% of currently healthy subjects younger than 50 had more than 15 disturbed breathing events in an hour of sleep, whereas 50% of individuals older than 65 had 15 or more events an hour.

In the oldest group, the respiratory disturbance index was 32.5 events per hour of sleep.

The increasing breathing disturbance index with age was also associated with a concomitant lower minimum arterial oxyhemoglobin saturation level.

In a comparison of the frequency distributions of breathing events between age groups, five of six comparisons showed significant advances with age (all P values

Men had a higher disturbance index (median 10) than women (median 5). The effect of age on the sleep disturbance index was similar in men and women, although no formal analysis was possible given the small number of individuals, the researchers reported.

Snoring, along with daytime sleepiness and obesity, are among the primary signs of sleep disorders used by physicians, the researchers wrote.

But in a secondary analysis of 51 individuals who reported no snoring and little or no significant daytime sleepiness and who were not overweight, the correlation between age and the respiratory index remained unchanged (P

In reviewing the study's limitations, the researchers noted the possibility that older individuals may underreport their symptoms in comparison with younger individuals who may have been screened out at the start because of reported symptoms. But this was unlikely, they said.

The arousal index appeared high in this study, even in the younger group, yet excluding almost half of the individuals who displayed some snoring or apnea did not alter the mean arousal rates in the remaining individuals, the investigators said.

Because the criteria used in the study did not distinguish between hypopneas associated with arousal and those associated with arterial oxyhemoglobin desaturation alone, it is possible that a change in baseline oxygenation could have contributed to the higher respiratory index in the older group, the researchers wrote.

Also, they said, the technologists reading the polysomnograms were not blinded to the volunteers, especially to their age, possibly imparting bias.

Discussing the clinical implications of a high respiratory disturbance index without symptoms or signs of obstructive sleep apnea, the researchers said that the clinical relevance of their findings is not clear.

It is possible, they said, that sleep fragmentation with age may lead to larger breaths at the time of arousal and smaller breaths or even central apneas at sleep onset, irregularities that could be misinterpreted as obstructive hypopneas.

If an increase in respiratory disturbances during sleep reflects a normal aging process and not pathologic breathing changes, then the clinical consequences should be adjusted by age.

However, Dr. Shea said, a high level of respiratory disturbances often leads to pathophysiologic consequences, including an increased risk of cardiovascular disease.

For example, the researchers said, it is unclear from these data whether the healthy individuals with high rates of respiratory disturbances may have had subclinical abnormalities that would eventually have an adverse affect on health.

Thus, in certain cases, treatment for sleep apnea should be considered on the basis of the respiratory disturbances alone, they said.

Definitive answers to the clinical necessity for obstructive sleep apnea screening and therapy in asymptomatic individuals, as well as determination of a normal respiratory disturbance index by age and sex, still awaits longitudinal studies of health outcomes in treated and untreated individuals, the researchers concluded.

Overnight sleep recordings and scoring of sleep studies were done with identical procedures at three laboratories operated by Sleep Health Centers, in Newton, Bedford, and Malden, Mass., and affiliated with Brigham & Women's Hospital, in Boston. The Newton laboratory was the site of data analysis and is accredited by the American Academy of Sleep Medicine.

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